Electrostatic spinning head

ABSTRACT

An improved spinning head for an electrostatic spinning apparatus including means for reinforcing and stabilizing the electrostatic field through which textile fibers are caused to travel so as to produce and maintain a desired flow path of said fibers therethrough to the twisting device carried within said spinning head.

United States Patent Amato [54] ELECTROSTATIC SPINNING HEAD [72] inventor: Richard A. Amato, Bolton, Mass.

[73] Assignee: North American Rockwell Corporation, Pittsburgh, Pa.

[22 Filed: Nov. 10,1970

[211 Appl.No.: 88,405

[52] [1.8. CI. ..57/58.89 [51] Int. Cl. ..D01h 1/12 [58] Field of Search ..57/58.89, 58.95

[56] References Cited UNITED STATES PATENTS 3,552,112 1/1971 Chabot ..57/58.89 X

POWER Sounca 51 Oct. 24, 1972 3,411,284 11/1968 Corbaz et al. ..57/58.9l 3,492,804 2/1970 Landuehrkamp et al ..57/58.95 X

Primary Examiner-John Petrakes Attorney-John R. Bronaugh, Floyd S. Levison, Dennis OConnor and Richard A. Speer ABSTRACT An improved spinning head for an electrostatic spinning apparatus including means for reinforcing and stabilizing the electrostatic field through which textile fibers are caused to travel so as to produce and maintain a desired flow path of said fibers therethrough to the twisting device carried within said spinning head.

4 Claims, 1 Drawing Figure PATENTEDUBT 24 m2 For POWER SOURCE ELECTROSTATIC SPINNING HEAD BACKGROUND OF THE INVENTION thence guided and impelled into the receiving end of o the spinning head that includes means for twisting and spinning said fibers into yarn.

In known electrostatic spinning devices, such as that shown in US. Pat. No. 3,411,284, issued Nov. 19, 1968 to A. Corbaz at al. for Method and Apparatus for Spinning Textile Fibers, the electrostatic field extends across an air gap between a drafting arrangement that mechanically advances the fibers into the field and a spinning head for twisting and spinning the fiber to form yarn. The fibers are fed into the drafting arrangement in the form of roving or sliver and are discharged therefrom as a stream of discrete fibers into the electrostatic field. The field is efiective in aligning the fibers and defining a flow path which the fibers are caused to follow to the spinning head.

Reliability of spinning fibers by the electrostatic process is dependent upon the strength and stability of the electrostatic field, and upon minimization of air turbulence created by the twisting device in the area of its fiber-receiving end.

In the present invention, the field between the receiving electrode and ground is reinforced in the fiber transport zone by partly filling the air gap between the electrodes with a dielectric material surrounding the receiving electrode. When the dielectric material conforms to an equipotential surface, there are no voltage gradients along the dielectric surface and, therefore, no tendency to build up charge accumulations. These accumulations tend to distort the field and become transient in nature by appearing and disappearing as surface'resistivity changes because of humidity or contamination. Air turbulence in the area of the fiber-receiving end of the twisting member increases fiber waste by deflecting the fibers from their intended path of travel.

The dielectric material located and formed according to the instant invention increases substantially the reliability of electrostatic spinning of textile fibers by providing a means which reinforces the electrostatic field and shapes it to facilitate focusing of the fibers toward the receiving end of the twisting device as well as stabilizing the field configuration by minimizing transient charge accumulations in the area adjacent to the fiber receiving end. Additionally, this body of dielectric material further enhances the reliability of this form of spinning by mitigating to a large extent the air turbulence in the area surrounding the fiber receiving end of the twisting member.

SUMMARY OF THE INVENTION The fiber-receiving end of the spinning head is made of a dielectric material and is disposed so as to protrude from an annular, high voltage electrode having an armated field generating surface which provides a converging electrostatic field and maximum field focusing and strength. A yarn gripper is rotatably carried within a support housing having a cap of dielectric fixed to the upper end thereof. The cap includes a centrally disposed through opening within which the gripper is rotated and the fiber receiving end thereof is disposed so that its surfaces ex't'end substantially continuous with the exposed dielectric surface of the cap. By providing only sufficient clearance for the fiber receiving end of the twisting device or so-called gripper spindle to rotate within the through opening of the cap, the air turbulence in this area is minimized. I

The outer surface of the cap is substantially identical in configuration to the underlying electrode and being made of a dielectric material it strengthens the field in the fiber transport zone while maintaining the direction of the field vectors. By shaping the dielectric surfaces of the cap to correspond to the equipotential surfaces of the field, there is no resultant change in the direction of the electric field vectors. This increased field strength provides improved fiber control at no increase in overall voltage. The cap configuration also permits the field lines to pass through its dielectric surface normally which maintains a stable field configuration, thereby reducing substantially the possibility of defocussing these lines and creating charge accumulations that would be transient in nature.

It is a general object of the invention to provide an improved spinning head for an electrostatic spinning apparatus capable of producing a strong, stable field configuration within which textile fibers are aligned and transported to the means for twisting and spinning them into continuous strand material.

A more specific object of the invention is to provide an improved spinning head for an electrostatic spinning apparatus which in addition to producing a strong and stable field provides improved fiber control, substantially reduced transient charge accumulation due to potential gradients along its surface and minimal turbulence in the area of the fiber-receiving end of the twisting device.

These and other objects of the present invention will become more fully apparent by reference to the appended claims and as the following detailed description proceeds in reference to the single FIGURE.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE is a partially schematic longitudinal section of the improved spinning head according to the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT The improved spinning head is identified generally in the drawing by numeral 10 and includes a support housing having a normally stationary body portion 11 and end caps 12 and 13 mounted respectively on the upper and lower ends of the body portion 11. A twisting device or so-called spindle 14 is journaled in the body portion 11 by axially spaced aligned anti-friction bearings 15 and 16 fixed within a central through bore 17 in the body portion 11. Body portion 11 has a laterally extending side opening 18 to an enlarged central portion 19 of the spindle 14 which is frictionally driven by an endless belt 20 extending through opening 18 and continuously rotated by a drive portion of the spinning apparatus (not shown).

Spindle 14 has an axial bore 21, the lower end of which defines a yarn discharge opening 22 from which spun yam (not shown) is drawn by take-up or drawing rolls 23 and 24.

The upper end of the spindle 14 is counterbored at 25 to receive a gripping member 26 into which fibers (not shown) are directed to be twisted and spun into yarn. Gripper member 26 may, for example, be one of the types illustrated in U.S. Pat. No. 3,372,537 issued Mar. 12, 1968 to M. Poull et al. for Radially Clamping Grips.

The upper end of the spindle 14 has an extension 27 defining a conical fiber inlet opening. This extension is made of a dielectric material and is positioned for rotation within a centrally disposed through opening 28 in the cap 12.

The fiber-receiving end of extension 27 has a funneled-shaped aperture 29 terminating in a cylindrical opening 30 in axial alignment with and substantially equal in diameter to the inlet end of the gripper 26. The adjacent end of gripper 26 is normally conductive while the extension 27 is of a dielectric material. A yarn tail (not shown) extends through opening 30 from gripper 26 into the aperture 29 and fibers from the supply source, a portion of which is depicted by rolls 31 and 32, are captured and presented to the yarn as the tail rotates through the maximum field where the tail is maintained. The surfaces of the funneled shaped aperture 29 are smooth and continuous so as to minimize electrostatic charge accumulations thereon. The top peripheral edge of this funneled aperture 29 is in close proximity to the wall of the through opening 28 provided in the cap 12, which is also of dielectric material, so as to provide a minimum amount of clearance between these two elements. With this closeness of assembly, the surface of the funneled opening 29 extends substantially continuous with the outer exposed surface of the cap and the possibility of air turbulence created by the rotation of the spindle 14 is substantially eliminated.

The annular metallic negative electrode, or cathode of the electrostatic system is shown at 33 and is fixed within the body portion 11 of the spinning head in axially aligned surrounding relation to the spindle 14 below the cap 12. This electrode 33 is connected by a lead 34 to a terminal of high voltage electrostatic power supply, the other terminal of which is grounded. The upper external surface of electrode 33 provides the field generating surface and is arcuated to define a segment of a sphere for maximum field focusing and strength. The metallic upper end of the gripper 26 in effect forms a continuation or extension of electrode 33, thus effectively providing a substantially hemispherical cathode.

The configuration of the electrostatic field is represented by dotted lines 35 as it extends from the outer dielectric surface of the cap 12 to the metallic portions of the rolls 31 and 32 that provide the ground for the electrostatic field. Cap 12 is annular, coaxial with spindle 14 and has an arcuated external surface which defines a segment of a sphere substantially concentric with the center of the spherical surface of the electrode 33 so that its exposed dielectric surface is approximately normal to the field lines.

As disclosed in the aforesaid Corbaz et al. US. Pat. No. 3,41 1,284 the electrostatic spinning process uses a high voltage electrostatic field to propel fibers into a rotating funnel. The surrounding negative electrode, or cathode, within which the funnel is coaxially joumaled preferably approximates a small hemisphere as disclosed herein for maximum field focusing and strength. The funnel (spindle extension 27) is made of a dielectric material and necessarily protrudes axially from the electrode 33. As disclosed herein, it is surrounded by a dielectric cap 12 to reducedisruptive air turbulence.

An improperly designed cap, such as a cup configuration, would tend to defocus the field in the spinning zone. The cap 12 is designed so that, in addition to reducing the air turbulence, it assists in providing the proper field shape.

By designing the cap 12 with dielectric surface corresponding to equipotential surfaces, there is no significant resultant change in the direction of the electric field vectors.

As shown in the drawing, the equipotential surfaces 36 at various radial distances from the hemisphere corresponding to the top of the funnel inlet of the spindle extension 27 are approximately concentric spheres. The hemispheric cap 12 is designed to correspond to an equipotential surface as closely as possible under usual manufacturing procedures. Design of cap 12 in this form is beneficial from the standpoint of field focusing, as already mentioned and additionally the field strength in the air gap between the rolls 31 and 32 and the electrode 33 is increased. If the surface of the dielectric corresponds exactly to an equipotential surface, the field strength is increased by the factor:

where V is the value of the equipotential surface before the dielectric is added, and V is the total potential difference between electrodes and e is the dielectric constant. Most solid dielectrics ha ve dielectric constants between 2 and 8. For the dimensions and dielectric values used (F 3 to 4) this enhancement was estimated to be almost a factor of two. This increased field strength is beneficial to the process. It permits improved fiber control at a lower overall voltage.

A third benefit results from the fact that the field lines 42 pass through the dielectric surface normally. Should the field lines emerge at some angle different from there would be a component field strength tangential to the dielectric surface. Because of the finite conductivity of this surface this would result in a current which in turn, wouldcreate charge accumulations at certain locations on the cap. These accumulations would produce additional distortion of the field. They would be transient in nature, appearing and disappearing as surfaces resistivity changed because of humidity or contamination. The cap 12 eliminates this problem. Such transient localized charge accumulations will not occur, and hence the field configuration will remain stable.

To summarize the operation, the rolls 31 and 32 are part of a conventional drafting system into which textile fibers are fed in the form of roving or sliver. The

fibers are discharged from between the rolls 31 and 32 as a stream of discrete fibers and immediately enter the electrostatic field which is effective to align and transport them to the fiber-receiving end of the spindle 14. The dielectric cap 12 forming a part of the invention has a configuration which corresponds to the equipotential lines of the electrostatic field and is effective, in addition to providing the desired field shape to strengthen and stabilize the field, thereby providing substantially improved control of the fibers. The fibers after entering the receiving end of the twisting member are received by the gripper 26 that is effective to twist and spin them into yarn. The yarn is drawn from the spindle 14 through its discharge opening 22 by means of the rolls 23 and 24 and is wound upon any suitable spool or the like not shown.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A spinning head for receiving textile fibers from a supply source and spinning them into yarn comprising:

a. a support housing having a body portion,

b. electrode means mounted within said body portion for establishing an electrostatic field for guiding and impelling fibers into said body portion,

c. a fiber twisting device carried within said body portion including a fiber inlet end to receive fibers transported by the field and a yarn discharge end,

d. means intermediate the ends of the twisting device for gripping the fibers and spinning them into yarn, and

e. a dielectric cap member carried on said body portion which is fabricated from a dielectric material and which has a configuration substantially conforming to the equipotential surfaces of the electrostatic field produced by the electrode means.

2. The spinning head defined in claim 1 wherein said further means for establishing an electrostatic field includes an annular electrode surrounding said twisting device having an arcuated field generating surface.

3. The spinning head defined in claim 1 wherein said means for effecting rotation of said twisting member includes a concentric driving roller integrally formed intermediate the ends of said twisting member and disposed within a channel in said support housing extending normal to the axis thereof whereby a driving belt passing through the channel is adapted to make frictional driving contact with said driving roller.

4. The spinning head defined in claim 1 wherein the fiber inlet end of said twisting member is of funneled configuration having a smooth continuous surface for minimizing electrostatic charge accumulations thereon.

Dedication 3,699,765.R2'0hm"d A. Amato, Bolton, Mass. ELECTROSTATIC SPIN- N ING HEAD. Patent dated Oct. 24, 1972. Dedication filed Mar. 23, 1977, by the assignee, EZec-tmspin Gorpomtz'on. Hereby dedicates to the Public the entire term of said patent.

[Ofiioial Gazette May 10, 1.977.] 

1. A spinning head for receiving textile fibers from a supply source and spinning them into yarn comprising: a. a support housing having a body portion, b. electrode means mounted within said body portion for establishing an electrostatic field for guiding and impelling fibers into said body portion, c. a fiber twisting device carried within said body portion including a fiber inlet end to receive fibers transported by the field and a yarn discharge end, d. means intermediate the ends of the twisting device for gripping the fibers and spinning them into yarn, and e. a dielectric cap member carried on said body portion which is fabricated from a dielectric material and which has a configuration substantially conforming to the equipotential surfaces of the electrostatic field produced by the electrode means.
 2. The spinning head defined in claim 1 wherein said further means for establishing an electrostatic field includes an annular electrode surrounding said twisting device having an arcuated field generating surface.
 3. The spinning head defined in claim 1 wherein said means for effecting rotation of said twisting member includes a concentric driving roller integrally formed interMediate the ends of said twisting member and disposed within a channel in said support housing extending normal to the axis thereof whereby a driving belt passing through the channel is adapted to make frictional driving contact with said driving roller.
 4. The spinning head defined in claim 1 wherein the fiber inlet end of said twisting member is of funneled configuration having a smooth continuous surface for minimizing electrostatic charge accumulations thereon. 